Warranty Cost Research Articles

Incremental cost of complications in colectomy: a warranty guided approach to surgical quality improvement

BackgroundWe assessed the warranty cost for colectomy at a single institution, as defined by the additional cost of treating complications distributed across all patients treated. MethodsAll segmental colectomies from July 8 to June 12 were reviewed for 0, 1, 2, and ≥3 complications. Warranty cost is defined as follows: ([mean additional cost of the case with complication(s) – mean base case cost] × number of episodes)/total population. ResultsThousand four hundred twenty-two colectomies were analyzed. The lowest cost case was a laparoscopic resection with 0 complications ($7,739 ± 4,150). Warranty costs were less for laparoscopic versus open colectomy (0 - $0, 1 - $128, 2 - $66, ≥3 - $248 vs 0 - $1,036, 1 - $501, 2 - $520, ≥3 - $1,971). This was true for costs associated with readmission ($303 vs $1,519). Emergency status and elderly status also impacted warranty costs. ConclusionsThe data demonstrate that warranty costs were highest with open colectomy, emergency cases, and the elderly. These data can be used to measure both quality and cost impact of mitigation strategies.

Structural optimization of an asymmetric automotive brake disc with cooling channels to avoid squeal

Brake squeal is still a major issue in the automotive industry due to comfort complaints of passengers and resulting high warranty costs. Many measures to avoid squeal have been discussed in the engineering community reaching from purely passive measures like the increase of damping, e.g. by the application of shims, to the active or semiactive suppression of squeal. While active measures can be effective but are elaborate and therefore more expensive, passive measure are less complex in most cases. This leads to the necessity to develop passive, economic and robust measures to avoid squeal. Asymmetry of the brake rotor has been proposed to achieve this goal and the resulting split of all double eigenfrequencies of the brake rotor has lately been shown to stabilize the system. Thus, a structural optimization of an automotive brake disc with cooling channels is presented in this paper with the objective to split all eigenfrequencies of the brake rotor in a certain frequency range by introducing asymmetry to the cooling channels. Constraints of the optimization are balance constraints, to guarantee a balanced operation for all rotor speeds, and minimal and maximal distance constraints of the cooling ribs, due to cooling and material strength requirements. First, a modeling approach of the brake disc with cooling channels is shortly presented which helps to avoid remeshing during the structural optimization. The introduced optimization problem is known to be highly nonlinear, nonconvex and with many local optima to be expected. Therefore, two approaches for the solution of the problem are chosen. The first, a deterministic one, is a Sequential Quadratic Programming (SQP) approach efficiently targeting local optima. In order to increase the possibility to find the global optimum, a set of randomly distributed starting configurations is chosen, leading to satisfying results. The other, a heuristic approach, uses a Genetic Algorithm (GA) directly aiming for the global optimum. The GA also delivers very satisfying results, nevertheless, the best solution has been found with the SQP approach. In order to validate the basic idea that a defined separation of eigenfrequencies helps to avoid squeal, modal analysis and squeal tests have been performed with a simplified disc with radial holes. The conducted experiments strongly support the theoretical findings and demonstrate the superior squeal behavior of the optimized disc.

Reliability Meets Big Data: Opportunities and Challenges

ABSTRACT Reliability field data such as that obtained from warranty claims and maintenance records have been used traditionally for such purposes as generating predictions for warranty costs and optimizing the cost of system operation and maintenance. In the current (and future) generation of many products, the nature of field reliability data is changing dramatically. In particular, products can be outfitted with sensors that can be used to capture information about how and when and under what environmental and operating conditions products are being used. Today some of that information is being used to monitor system health and interest is building to develop prognostic information systems. There are, however, many other potential applications for using such data. In this article we review some applications where field reliability data are used and explore some of the opportunities to use modern reliability data to provide stronger statistical methods to operate and predict the performance of systems in the field. We also provide some examples of recent technical developments designed to be used in such applications and outline remaining challenges.

Preventing Drum Brake Squeal through Lining Modifications

Drum brake squeal is one of the most common and annoying types of brake noise and it usually falls in the frequency range between 0.5-16 kHz. Brake squeal continues to confront vehicle manufacturers where it not only leads to significant increase in the warranty costs but also may affect customers perception on quality of the vehicle. Thus this paper attempts to prevent drum brake squeal by means of lining modifications. In doing so, finite element method is first employed and squeal noise will be then predicted using complex eigenvalue (CE) analysis. A good lining modification should be able to stabilize the drum brake assembly by shifting or reducing positive real parts toward zero or negative real parts in the eigenvalue analysis. Finally, laboratory squeal tests are conducted on the four proposed modifications to verify its effectiveness against squeal.

RELIABILITY IMPROVEMENT METHODOLOGY FOR CONSUMER PRODUCTS - A CASE STUDY

The objective of every industry is to bring world-class quality products to the market in shortest possible time with least expenses. To meet this objective manufacturer’s always remains non compliant with Reliability requirement of the products due to which field failure rate increases and in turn increases the warranty cost. In this work, an attempt has been made to improve the field reliability for consumer product through a proposed step by step Reliability Improvement Methodology. The proposed methodology includes analysis of field failure data, failure analysis for identifying root cause, experimental investigation to confirm root causes, design modification recommendations and improvement validation through accelerated testing. Further, this analysis helps the manufacturers in warranty extension decision making for the existing products and in the improvement of the next generation product’s performance which directly increases the brand image and profits of an organization.

A new replacement warranty policy indexed by the product’s correlated failure and usage time

We study a new warranty policy for non-repairable products which is indexed by two correlated random variables, age and usage and covers all failures in (0,t]. Two different warranty costs for the replacement of the failed product are considered, according to its usage being greater or less than a pre-specified level s>0. A bivariate probability distribution function is applied to incorporate the correlation effect of the two variables. Analytical expressions of the probability density function of the total warranty cost and its expected value, the probability distribution functions of the number of the failed products with usage greater or less than s and their corresponding expected values and costs are derived. Limit results are also obtained. The results obtained are useful measures in establishing the compensation policy and the evaluation of its performance under the proposed warranty. Illustrative numerical examples of the expected cost for Paulson, Pareto and Beta Stacy bivariate distributions are presented and discussed. In particular for Paulson’s bivariate probability distribution, closed form expressions for the expected costs are obtained.

Detecting Groan Sources in Drum Brakes of Commercial Vehicles by TVA-FMEA: A Case Study

In this article, the strategy followed by an automobile company for detecting the root causes of groan complaints related to rear drum brakes in commercial vehicles is presented using data collected from the sold troubled vehicles and from new vehicles from the production line, as well as the drum-brake test rig at the laboratory. Drum brake groan is often very intense and can cause large numbers of customer complaints. During a groan noise event, vehicle structure and suspension components are excited by the brake system and result in a violent event that can be heard and felt during brake application. This paper condenses experimental studies on a low frequency drum brake groan problem that has caused high warranty costs. First, the environmental conditions causing the groan were identified and the groan was reproduced. Vehicle tests were performed both at the factory and in traffic. To conclude the planned study, TVA (Total Value Analysis) and FMEA (Failure Mode and Effects Analysis) methods were used effectively. A strategy to determine the root causes was planned and implemented systematically to eliminate the secondary and tertiary effects of brake groan problems. In order to ge to the root causes, vibration and groan measurements were executed and interpreted according to TVA and FMEA charts. The sensitivity of the lining material of the brake shoes to different environmental conditions was investigated. Finally, the groan mechanism of the drum brake system is discussed and the solution to the low frequency drum brake groan problem is evaluated in detail.

OPTIMAL PRICE AND RELEASE TIME OF A SOFTWARE UNDER WARRANTY

The time of domination has ended. Competition is "in". To get prolonged huge profit in highly competitive markets, firms need some effective tools and techniques. An instrument for competitive advantage in such prevailing cut throat environment is product differentiation. The general differentiation factors can be the product or service offerings through the value added services or offerings through product extensions and one of the most important differentiating factors amongst all is product warranty. Warranty is seller assurance to a buyer that a product will carry out as stated and this promise works as a confidence for the buyer in purchasing the product. But servicing a warranty engages additional costs to the manufacturer and this has an effect on the profit levels. Warranty cost may be reduced by providing higher reliable product. The conflict existing in the context of software reliability, warranty period and selling price need to be considered jointly. In this paper, we develop an optimization model to determine the optimal price, time to stop testing under a given warranty period with constraint on reliability and sales of the software product so as to maximize the profit. Numerical examples have been done to illustrate the proposed model.

A methodology for design for warranty with focus on reliability and warranty policies

PurposeThe purpose of the paper is to develop a conceptual framework that integrates the technology and commercial issues early at the design stage to minimize warranty costs in the most effective and efficient manner and also to develop a model for optimization of warranty with specific focus on reliability and warranty policies.Design/methodology/approachThe critical issues in warranty are addressed which affect the warranty cost. An optimization model to achieve multiple goals like minimization of the warranty cost and improving the reliability of the product is developed using genetic algorithm as a solution methodology. The model is illustrated with a real case of automobile engine.FindingsThe results of the optimization show improvement in mean time between failures (MTBF) which results due to improvement in the product reliability and also the targeted warranty cost is achieved.Research limitations/implicationsThe model developed needs to be further extended with inclusion of additional decision variable such as support level offered and more objectives such as attractiveness of the warranty from the customer's view point and spares cost to the customer.Originality/valueThe paper provides the help to the designers at the design stage to take the decisions related to warranty in deciding the warranty parameters.

The role of pad-modes and nonlinearity in instantaneous mode squeal

Disc brake squeal is a major source of customer dissatisfaction and related warranty costs for automobile manufacturers. Although mode coupling is recognised as a mechanism often found in squealing brakes, recent research results show that friction induced pad-mode instabilities could be the cause of instantaneous mode squeal reported in the literature. In this paper, the nonlinear characteristics of instantaneous mode squeal initiated by pad-mode instabilities are studied by analysing phase space plots of vibrations and sound pressure for a numerical model of a pad-on-plate system as the friction coefficient increases. Results show that as the friction coefficient increases from 0.05 to 0.65, attractors of vibration in the phase space transits from limit cycle to quasi-periodic, showing signs of approaching chaotic behaviour. It is shown here that the correlation of the sound pressure behaviour in the phase-space with structural vibration is crucial to understanding the role of pad modes and nonlinearity in instantaneous mode squeal.

Warranty optimisation based on the prediction of costs to the manufacturer using neural network model and Monte Carlo simulation

Warranty is a powerful marketing tool, but it always involves additional costs to the manufacturer. In order to reduce these costs and make use of warranty's marketing potential, the manufacturer needs to master the techniques for warranty cost prediction according to the reliability characteristics of the product. In this paper a combination free replacement and pro rata warranty policy is analysed as warranty model for one type of light bulbs. Since operating conditions have a great impact on product reliability, they need to be considered in such analysis. A neural network model is used to predict light bulb reliability characteristics based on the data from the tests of light bulbs in various operating conditions. Compared with a linear regression model used in the literature for similar tasks, the neural network model proved to be a more accurate method for such prediction. Reliability parameters obtained in this way are later used in Monte Carlo simulation for the prediction of times to failure needed for warranty cost calculation. The results of the analysis make possible for the manufacturer to choose the optimal warranty policy based on expected product operating conditions. In such a way, the manufacturer can lower the costs and increase the profit.

Customized warranty offering for configurable products

Although configurable products have been common in the market, buyers often receive standard warranty offerings rather than customized ones from manufacturers. In this study, a reliability based method is proposed to specify warranties for certain product configuration schemes. A continuous time Markov model is adopted to measure the vulnerabilities of components involved in configuration. Then the warranty claim probability of a product with multiple components is calculated, and the warranty costs in varied warranty periods are estimated. Under a minimal repair warranty in which only failed components are replaced free of charge, warranty plans can be customized for different configuration schemes on the basis of warranty costs. Next, an example of laptop computer is introduced to illustrate the procedure and effectiveness of the proposed method. Impacts of operating frequency and operating time of products on warranty costs are also measured. In addition, some recommendations are provided in order to deal with issues of replacement policy, pro-rata rebate warranty (PRW) and compatibility between components.

Warranty implementation and evaluation: a global firm's case

Purpose – This case study aims to develop and empirically test a general framework for the implementation and evaluation of a warranty policy (i.e. implementation, support structure, and evaluation stages) within the context of a high‐tech global firm.Design/methodology/approach – The sample consisted of the employees of an anonymous US‐based global high tech firm.Findings – The findings for the implementation stage report that the cost and profit centers should have their costs allocated on the basis of activity. For the support structure, there is a negative response to outsourcing as an option for implementing the warranty policy. For the evaluation, findings report that US firms should reevaluate their pricing, quality, and warranty strategy for domestic and international markets.Research limitations/implications – This case study can be expanded by examining how companies balance the cost/quality/warranty ability of the product, the techniques used to allocate warranty costs, and to evaluate multiple...

One‐dimensional warranty cost analysis for second‐hand items: an overview

PurposeThe purpose of this paper is to review and develop stochastic models for the evaluation of the expected warranty cost, from dealer's viewpoint, for second hand items sold under different warranty policies.Design/methodology/approachThis study makes a useful contribution to the warranty literature by developing a framework to study one dimensional warranty policies for second‐hand products from dealer's viewpoint. Also, numerical examples are provided to illustrate the application of these models.FindingsDespite the fact that warranties for second‐hand products are commonly used, the accurate pricing of warranties in many situations remains an unsolved problem, for both the dealer and customer. The proposed framework allows the dealer to analyze the cost of alternative warranty policies before deciding on the policy to be offered with the sale of a second‐hand item.Originality/valueThe policies and models developed in this paper can be useful in managerial decisions making related to second‐hand products such as automobiles, home appliances, helicopters, electronic equipment and electronics.

Optimal Unlimited Free-Replacement Warranty Strategy using Reconditioned Products

The long-term sustainability of our resources is dependent on reducing the consumption of virgin resources, and one method of achieving this goal is product remanufacturing. It is already established that the production of remanufactured products costs less than that of creating a new one, however the effects of this on warranty costs are now considered. Due to consumer perceptions of the quality of remanufactured products, it cannot be sold for the same price as a new product. In addition, the warranty costs the manufacturer incurs will also be higher. This paper proposes a mathematical model for the optimal one-dimensional unlimited free-replacement warranty policy with replacements carried out with reconditioned products. Numerical optimization is used to compute the optimal warranty and production parameters which maximize the total profit.

주기적인 유지보수 계획에 따른 중고제품에 대한 최적 향상수준

Due to a growing demand for the second-hand product, especially for the expensive one, the warranty and maintenance policies for such products have been studied to improve the product reliability of late. In this paper we study a periodic maintenance model for the second-hand product which is purchased by the customer at the age of . When purchased, the dealer provides a warranty of a fixed length during which the product is maintained periodically to reduce the failure rate of the product and thus, to improve the reliability after each maintenance is served. If a failure occurs between two successive maintenances, only minimal repair is conducted. As for the warranty policy, we adopt free non-renewing repair action on each failure, in addition to the periodic maintenance service during the warranty period. Thus, under the given warranty policy, all the maintenance and repair costs incurred during the warranty period are charged to the dealer. For the proposed periodic maintenance scheme, we formulate a cost model to evaluate the expected total cost charged to the dealer during the warranty period and derive an optimal upgrade level of the failure rate at each maintenance to minimize the expected total warranty cost from the perspective of the dealer. We also present numerical results for an optimal upgrade level based on the proposed methods.

Optimal release policies for a software system with warranty cost and change-point phenomenon

Determining the software quality and release time of the software is an important role of software reliability. Software reliability growth models (SRGMs) are applications of software reliability. The change-point is defined as the prominent change in the software testing time, in connection with the quality of a software error occurrence or error-detection phenomenon. As a result, the software reliability growth process, based on the change-point, affects the precision of the software reliability prediction, based on the SRGMs. To find the accurate total expected delivery cost with a suitable warranty period of the software system, a new cost model for the software system with the warranty and change-point phenomenon is proposed in this paper. The entire expected delivery cost and the reliability of the software system is calculated using the change-point SRGM. The optimal release time is calculated by reducing the overall estimated delivery cost for various desired reliability levels. Based on the proposed warranty cost model and the reliability of the software system, we have derived some optimal release policies. Numerical illustrations and interconnected discussed data are itemized. From the testing outcome, we get software release policies that provide a comprehensive analysis of software based on the total expected delivery cost with a suitable warranty period, desired level of reliability, and change-point. Moreover, these policies will be helpful for project managers to decide where to stop the testing for customer release at the exact time with a suitable warranty period.

Heuristics for Design for Reliability for Electrical and Electronic Products

Incomplete specifications on new products are very common resulting in unreliable products and costly scope creeps and design changes. Designing out failures using lessons learned can result in very high reliability and significantly lower warranty costs. The quickest way to make use of the lessons learned is to learn from heuristics which are short statements based on wisdom from lessons learned over many products. The article covers examples to show how the heuristics were applied to successful products.

Multi-step Functional Process Adjustments to Reduce No-fault-found Product Failures in Service Caused by In-tolerance Faults

This paper proposes a methodology to eliminate or reduce No-Fault-Found (NFF) Product failure in field by adjusting manufacturing processes. No-Fault-Found (NFF) failures can be frequently characterized by in-tolerance faults, i.e., faults occur when design parameters represented by Key Product Characteristics (KPCs) and process variables represented by Key Control Characteristics (KCCs) are within the tolerance limits (in-spec) and therefore they cannot be eliminated by standard process control and adjustment methods. Literature in the area of statistical process and control are unable to monitor and adjust the NFF failures as these methodologies are based on design template itself. Also, all the adjustments strategies consider in process adjustment domain are single-step or adjustments are performed instantaneously. However, the single-step adjustment from process nominal (ud) to functional nominal (uf) is not always possible due to presence of system or resource constraints limiting the amount of adjustment that can be made in a given time such scenario in this paper is refer as multi-step adjustment scenario. This paper proposes a methodology for the multi-step functional process adjustment by identifying the adjustment paths that will minimize the total cost associated with product failure and adjustment cost. The proposed methodology includes: (i) discretization of space from ud to uf, orthogonally, with defined resolution; (ii) identification of warranty cost at each discretised node based on overlap between manufacturing distribution and in-tolerance NFF regions considering node as production nominal; and (iii) determination of the multi-step function process adjustment between ud and uf using recursive dynamic programming formulation. The methodology is illustrated through numerical simulation.

Warranty Data Evaluation

The article deals with a possible way how to monitor and evaluate warranty date. Tools that allow the current development of warranty costs and related indicators to be monitored and evaluated are outlined in the article. The tools proposed are applicable to the continuous (periodical) evaluation of real development and the detection of possible deviations, which can occur when comparing real and predicted development warranty data.